1. Field of the Invention
The present invention relates to a method and an apparatus for forming an electric circuit disposed on a construction member of a machine like a car. A forty-fifth aspect of the invention is the apparatus as described in the thirty-seventh aspect
2. Related Art
Referring to FIG. 19, a car 121 has electric appliances including lamps such as head lamps and tail lamps, motors like a starter motor and an air-conditioning motor, etc.
As illustrated in FIG. 20, the car 121 has a door 113 mounted with a speaker 115, a power window switch unit 116, a door lock unit 117, and a power window motor (not shown). The door 113 further has a door panel 114 made from a metal sheet and a door trim panel 112 arranged inside the door panel 114. The door panel 114 and the door trim panel 112 are construction members of the car 121.
On one of the door panel 114 and the door trim panel 112, there are disposed the speaker 115, the power window switch unit 116, the door lock unit 117, and the power window motor. The speaker 115 receives sound signals for a car stereo player to provide audio sounds to occupants in the car 121.
The power window switch unit 116, which is operated by an occupant, moves upward and downward a door glass. The power window switch unit 116 also makes the door lock unit 117 lock and unlock the door 113. The power window motor, which is operated by the power window switch unit 116, moves the door glass of the door 3.
The door 113 of the car 121 is arranged with a wiring harness 100 (see FIG. 20) for providing an electrical power and control signals to the speaker 115, the power window switch unit 116, the door lock unit 117, and the power window motor. The wiring harness 100 has a plurality of electrical cables composing electric circuits, connectors 101, 102, 103, 104, and 105 fitted to the cables at desired positions, protectors 106, and clips 107. Each of the cables is a covered cable having conductor core wires and a covering insulating layer for covering the core wires.
The plurality of cables are tied in a bundle with tapes in a desired pattern and fitted with the protectors 106 and the clips 107 at predetermined positions to compose the wiring harness 100. The clips 107 secure the wiring harness 100 on the door panel 114 or the door trim panel 112 between the door panel 114 and the door trim panel 112.
The connectors 101, 102, 103, 104, and 105 each are coupled to an associated connector of a main wiring harness or each electric instrument 115, 116, or 117 which is mounted on a body 118 of the car 121.
The electrical connection of connectors 101, 102, 103, 104, and 105 with the associated connectors of the main wiring harness and the electric instruments 115, 116, and 117 enables to provide an electrical power and control signals to each of the electric instruments 115, 116, and 117. Thus configured wiring harness 100 is fitted on the door 113 to move upward and downward the door glass and to lock and unlock the door.
At a design step of the car 121, positions and sizes of construction members and parts are determined in the use of a three-dimensional coordinate system C having axes X, Y, and Z as illustrated in FIG. 19. The coordinate system can show any position of the whole body of the car 121. An origin of the coordinate system may be positioned at a desired position in the car 121.
A set of three-dimensional data D1 based on the coordinate system determines positions and sizes of construction members and parts of the car 121. The data D1 includes coordinates to position each electrical cable constituting the wiring harness 100, a length of the cable, and a cross-sectional area of the cable.
To fabricate the wiring harness 100 based on the three-dimensional data D1, first, a two-dimensional developed plan of each cable is provided. Next, electrical cables are cut each to have a desired length, and the cables constituting the wiring harness 100 are arranged on a wiring board 110 shown in FIG. 21. These electrical cables are tied in a bundle with winding tapes to provide a predetermined pattern, and the bundle of cables is provided with other fittings such as the protector 106 and the clip 107 to assemble the wiring harness 100.
The wiring board 110 is a plate having a flat surface. On the surface of the wiring board 110, there is drawn an arrangement pattern of the electrical cables including positions of the connectors 101 to 105 and other fittings such as the protector 106 and the clip 107. The wiring board 110 is provided with a plurality of locating pins 111 for positioning the electrical cables according to the arrangement pattern.
As described above, in the conventional forming method of the wiring harness 100, a two-dimensional drawing of each electrical cable of the wiring harness 100 based on the aforementioned data D1 is provided after a general design of the car 121. Then, electrical cables each having a desired length are arranged on the wiring board 110 to assemble the wiring harness 100.
The conventional forming method of the wiring harness 100 requires a large amount of man hours for preparing the two-dimensional drawings and cutting electrical cables each to have a desired length before the assembling of the wiring harness 100. Furthermore, test wiring harnesses for a new model of cars require a considerable amount of time and cost.